Study of IR absorption properties of fumed silica-opacifier composites

Mineral powders were added into fumed silica as IR opacifers in order to develop opacified thermal insulating composites for application at high temperatures up to 1000 °C. The opacifying effect was evaluated with effective specific extinction. The results indicated that opacifiers could effectively block IR radiation heat transfer and improve thermal insulating properties of fumed silica. Among four opacifiers investigated in this paper, SiC was proved to be the best one for excellent extincting performance. When SiC was adopted with average particle size of 3.029 μm and mass ratio of 25%, the values of effective specific extinction increased from less than 12.6 m2/kg to about 55 m2/kg in the wavelength range from 2.5 to 7 μm. It was demonstrated that fumed silica-opacifier composites are efficient high temperature insulating materials.